Quantification of road vehicle handling quality using a compensatory steering controller

Abstract

Criteria for stability and controllability of road vehicles are briefly reviewed and it is argued that there is a need for criteria that might better relate to subjective ratings by drivers. The variance of a driver's closed-loop control action against random disturbances acting on the vehicle is proposed as a realistic criterion that might relate to a driver's assessment of the vehicle. A nonlinear vehicle model with five degrees of freedom, negotiating a ninety-degree bend in minimum time is the basis for the theoretical study. The vehicle model is run with the centre of mass in two different positions. It is found that the variance of the driver's compensatory steering control varies significantly through the manoeuvre, reaching a peak at about mid-corner. The corresponding variance in the lateral path error of the vehicle also peaks at about the same position in the manoeuvre. Comparison of these variances to existing stability and controllability criteria shows that the variance of the compensatory control might reveal aspects of the handling behaviour that the existing criteria do not. Recommendations for further work are given, and include a program of driving simulator experiments or track tests to correlate the new criteria against subjective ratings by human drivers.